Here is a hypothetical scenario:
- Have Harm Cast on a player (reducing the maximum hit points)
- Cast Feign Death on the player, suppressing (not removing) the effects of the disease (not healing, but restoring the maximum hit points they have)
- Heal them (now that their maximum hit points are no longer reduced)
- Wake them up…
Does their hitpoint stay as they are (at maximum), or are they reduced back down (effectively taking damage again)?
If the target is diseased or poisoned when you cast the spell, or becomes diseased or poisoned while under the spell’s effect, the disease and poison have no effect until the spell ends.
If the target fails the saving throw, its hit point maximum is reduced for 1 hour by an amount equal to the necrotic damage it took. Any effect that removes a disease allows a creature’s hit point maximum to return to normal before that time passes.